Physiology · Reproduction, pregnancy and the fetus
Puberty !
- Regulation
- Exam priority: medium
Puberty begins when the brain restarts pulses of GnRH; the gonads wake up and the body matures sexually and grows fast.
Updated 2026-11-01
Also called: Tanner stages, Adrenarche, Gonadarche
See it in 3D: Hypothalamus · Pituitary gland · Testes · Ovaries · Mammary gland lobes · Left adrenal gland
What it is
The GnRH pulse generator is active in the newborn period (mini-puberty), then held back during childhood. Around age 8–13 in girls and 9–14 in boys, kisspeptin and other signals release that brake: night-time LH pulses appear first, gonadal steroids rise and secondary sexual characteristics follow in a predictable order. Adrenal androgens rise separately (adrenarche).
Hormone axes and feedback
Hypothalamic–pituitary–ovarian axisLesion None (normal)
Tap a box to see the hormone, or choose a lesion to see the lab pattern.
- Stimulates (+)
- Inhibits / negative feedback (−)
- Positive feedback (high E₂ at mid-cycle)
- Level ↑
- Level ↓
Hormone axes and feedback
Lesion Functioning gonadotroph adenoma (rare)Pattern GnRH ↓ · LH ↑ · FSH ↑ · Testosterone ↑ · Inhibin B ↑
Secondary hyperfunction: Functioning gonadotroph adenoma (rare)
Pattern: GnRH ↓ · LH ↑ · FSH ↑ · Testosterone ↑ · Inhibin B ↑
A pituitary adenoma raises its hormone and the gland hormone; the hypothalamus is suppressed. LH/FSH ↑ and testosterone ↑. In children, central precocious puberty gives the same pattern, driven from GnRH.
Exam rule: if the pituitary hormone moves opposite to the gland hormone, the problem is in the gland (primary); if they move together, it is central (pituitary or hypothalamus).
- Stimulates (+)
- Inhibits / negative feedback (−)
- Level ↑
- Level ↓
Regulation
- +Kisspeptin (KISS1R), neurokinin B: Restart the pulsatile GnRH release that defines puberty.
- +Leptin and adequate energy stores: Permissive signal that the body can afford reproduction.
- −Central inhibitory tone (GABA) during childhood: Keeps GnRH pulses low between mini-puberty and puberty.
- −Undernutrition, chronic illness, intense exercise, hypothyroidism: Delay puberty (functional hypogonadotropic state).
- +Adrenal androgens (DHEA-S, adrenarche ≈6–8 years): Pubic and axillary hair, body odor; independent of the gonadal axis.
Order of events
| Step | Girls | Boys |
|---|---|---|
| First sign | Breast buds (≈8–13 years) | Testes ≥4 mL (≈9–14 years) |
| Then | Pubic hair | Pubic hair, penile growth |
| Growth spurt | Early (Tanner 2–3) | Late (Tanner 3–4) |
| Late event | Menarche (≈12–13 years) | Voice change, facial hair, spermarche |
Clinical notes
- Kallmann syndrome: GnRH neurons fail to migrate with olfactory neurons; delayed puberty with low LH and FSH plus anosmia.
- Congenital adrenal hyperplasia and estrogen- or androgen-secreting tumors cause peripheral precocious puberty with suppressed gonadotropins.
- Constitutional delay of growth and puberty is the most common cause of late puberty in boys; bone age is delayed and puberty eventually completes.
Test yourself
Think of the answer, then tap the question to see it.
A 6-year-old girl has breast development. LH rises clearly after a GnRH stimulation test. Central or peripheral?
Central (GnRH-dependent): the hypothalamic–pituitary axis has switched on early, so gonadotropins respond. Peripheral precocity would show suppressed LH.
Why are men taller on average than women at the end of puberty?
Boys start puberty later and their growth spurt comes later (Tanner 3–4), so they have more prepubertal growth years, plus a larger spurt, before estrogen closes the plates.
Why can anorexia nervosa or very intense athletic training delay menarche?
Low energy stores and low leptin suppress GnRH pulses, so LH, FSH and estradiol stay low (functional hypothalamic hypogonadism).
See it in 3D
The structures of Durgical's 3D anatomy where it happens.
Related topics
- The male gonadal axis and spermatogenesis
- The menstrual cycle: ovary and endometrium
- Growth hormone and IGF-1
- Testosterone and its actions
- Actions of estrogen and progesterone
Related conditions
Educational physiology content; not a diagnostic or treatment guide and no substitute for a health professional's advice. Values are approximate references. No doses are given.
Sources: 27.3 Development of the Male and Female Reproductive Systems (OpenStax (Rice University), 2022); 17.11 Development and Aging of the Endocrine System (OpenStax (Rice University), 2022); Hall JE. Guyton and Hall Textbook of Medical Physiology, 13th ed. (ch. 82). Reference book used to check facts; its text and figures are not reproduced (Elsevier, 2016).
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Representative model, for educational purposes only.